1. Field of the Invention
The present invention relates to a circular loom for producing a tubular woven fabric and, more particularly, to a mechanism for stopping the driving of the circular loom in accordance with a signal issued from a mechanism for detecting an abnormal condition of a weft taken out from a shuttle in the circular loom. The mechanism for automatically stopping a circular loom due to an abnormal condition of a weft taken out from a yarn package formed on a bobbin held by a shuttle during the weaving operation is hereinafter referred to as the mechanism for stopping a circular loom during the weaving operation thereof.
2. Description of the Prior Art
In a circular loom, a shuttle is moved along a circular running passage, and a weft taken out from the shuttle is inserted into successive sheds created in advance of the arrival of the shuttle, and the weft is interwoven with warps to form a tubular woven fabric. However, the conventional circular loom of this type includes a serious problem. Namely, when the weft is broken or a yarn package formed on a bobbin held by a shuttle is exhausted, the weft insertion into the successive sheds is interrupted, even though the shuttle travels along the circular running passage formed in the circular loom. Therefore, such an interruption of the weft-insertion into the successive sheds creates a portion of tubular fabric without weft and, consequently, it has been necessary to have a machine operator continuously watch the weaving operation. In other words, the possibility of the occurrence of the above-mentioned problem prevents the rationalization of the production of tubular woven fabric by circular looms, which rationalization includes the reduction of the number of machine operators and production costs.
To eliminate the above-mentioned problem, several proposals for detecting weft-breakage or exhaustion of a yarn package formed on a bobbin held by a shuttle, during the weaving operation of a circular loom, have recently been put into practice. For example, in the circular loom manufactured by Starlinger & Co., Austria, a photo-electric device for detecting the exhaustion of the yarn package formed on a bobbin held by a shuttle is utilized. This device is mounted on the circular loom and comprises a light emitting device which emits a light beam directed to the passage of the shuttle, and a photocell for receiving a possible reflection from the surface of a bobbin, from which a weft has been exhausted. In another example, in the circular loom manufactured by ED Ferreirinna & Irmao, Portugal, a photo-electric device like the device utilized for the circular loom manufactured by Starlinger & Co., is applied. To detect weft breakdown during the weaving operation, a mechanical sensor to detect a weft break-down is mounted on a device for propelling a shuttle, and this mechanical sensor is capable of detecting a condition that a weft is not inserted into the successive sheds formed in the circular loom, and; when this mechanical sensor detects a weft break-down, an electric signal due to the detection by this sensor is transmitted to an actuator to operate a stop motion mechanism of the circular loom.
Based on the experience of the invention of the present invention, as well as research they conducted on the mechanisms of the above-mentioned devices, it has been determined that the mechanisms of the above mentioned devices are complicated, the working functions thereof are not stable and the reliability thereof is uncertain.
Therefore, it is the main object of the present invention to provide a practical mechanism for stopping a circular loom during the weaving operation when a detector detects a weft breakage or an exhaustion of a yarn package formed on a bobbin held by a shuttle, so as to eliminate the above-mentioned serious problem caused by the above-mentioned abnormal condition of weft taken from a yarn package formed on a bobbin held by a shuttle.